1. Field of the Invention
This invention relates to an electromagnetic trigger device in a motor-driven camera capable of effecting bulb exposure.
2. Description of the Prior Art
There has been proposed a motor-driven camera such as, for example, a cine camera which is provided with a member for stopping the shutter at the position where the shutter is kept opened (to be referred to as the opened shutter position hereinafter) in order to attain a long exposure time required under the low or poor lighting condition such as the exposure at night or the microscopic photography, and with a member for stopping the shutter at the position where the shutter is kept closed (to be referred to as the closed shutter position hereinafter). The motor-driven camera of type described are for instance disclosed in U.S. Pat. Nos. 3,721,492 and 3,722,989. However, with the camera described in U.S. Pat. No. 3,721,492, when a release button is operated for terminating a long time exposure, a shutter is closed, and the next frame of film is transported and successively the next exposure is initiated. Therefore, this camera is not advantageously adapted for use in the microscopic photography in which each frame must be exposed for a relatively long time, for instance 20 seconds, and the interval between the successive two exposures must be also longer, for instance 5 minutes. The camera disclosed in U.S. Pat. No. 3,722,989 has disadvantage in that consumption of the power source is remarkable because a current flows to an electromagnet during opening of the shutter even if a long exposure time is selected.